Distal access aspiration guide catheter

ABSTRACT

Distal access aspiration guide catheter system and methods for delivering implantable devices, catheters, or substances in or near and/or restoring flow through body lumens, such as blood vessel lumens are described. A Distal access aspiration guide catheter having a proximal, medial, and distal possessing high flexibility, high resistance to kinking and a large lumen to wall thickness ratio.

RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No. 13/878,890, entitled, “DISTAL ACCESS ASPIRATION GUIDE CATHETER,” which is national stage filing under 35 U.S.C. 371 of PCT/US2011/054600 filed Oct. 3, 2011, which claims priority to U.S. Provisional Patent Application No. 61/389,688 filed Oct. 4, 2010, the entire disclosure of each of which is expressly incorporated herein by reference.

FIELD OF THE INVENTION

The present invention relates generally to medical devices and methods and more particularly to catheter-based systems and methods useable for accessing, diagnosing, or treating defects in blood vessels, such as blood vessels of the brain.

BACKGROUND OF THE INVENTION

Pursuant to 37 CFR 1.71(e), this patent document contains material which is subject to copyright protection. The copyright owner has no objection to facsimile reproduction of the entire patent document or the patent disclosure, as it appears in the Patent and Trademark Office patent file or records, but otherwise reserves all copyright rights whatsoever.

Stroke is a common cause of death and disability. In the United States, approximately 700,000 patients suffer from stroke annually. Stroke is a syndrome characterized by the acute onset of a neurological deficit that persists for at least 24 hours, reflecting focal involvement of the central nervous system, and is the result of a disturbance of the cerebral circulation. Its incidence increases with age. Risk factors for stroke include systolic or diastolic hypertension, hypercholesterolemia, cigarette smoking, heavy alcohol consumption, and oral contraceptive use.

Hemorrhagic stroke accounts for 20% of the annual stroke population. Hemorrhagic stroke often occurs due to rupture of an aneurysm or arteriovenous malformation (AVM), causing bleeding into the brain tissue and resultant infarction of brain tissue. The remaining 80% of strokes are due to ischemia that occurs due to occlusion of a blood vessel that deprives brain tissue of oxygen-carrying blood. Ischemic strokes are often caused by emboli or pieces of thrombotic tissue that have dislodged and traveled from other body sites, or from the cerebral vessels themselves, to occlude in the narrow cerebral arteries more distally. When a patient presents with neurological symptoms and signs, which resolve completely within 1 hour, the term transient ischemic attack (TIA) is used. Etiologically, TIA, and ischemic stroke share the same pathophysiologic mechanisms and thus represent a continuum based on persistence of symptoms and extent of ischemic insult.

Emboli occasionally form around the valves of the heart or in the left atrial appendage during periods of irregular heart rhythm and then are dislodged and follow the blood flow into the distal regions of the body. Those emboli can pass to the brain and cause an embolic stroke. As will be discussed below, many such occlusions occur in the middle cerebral artery (MCA), although such is not the only site where emboli come to rest.

When a patient presents with neurological deficit, a diagnostic hypothesis for the cause of stroke can be generated based on the patient's history, a review of stroke risk factors, and a neurologic examination. If an ischemic event is suspected, a clinician can tentatively assess whether the patient has a cardiogenic source of emboli, large artery extracranial or intracranial disease, small artery intraparenchymal disease, or a hematologic or other systemic disorder. A head CT scan is often performed to determine whether the patient has suffered an ischemic or hemorrhagic insult. Blood would be present on the CT scan in subarachnoid hemorrhage, intraparenchymal hematoma, or intraventricular hemorrhage.

To reach these lesions or occlusions microcatheter and microguidewire must be employed, but often the column support of these microcatheters is not strong enough to navigate through the distal reaches of the neurovasculature to effectively treat these sites. Often guide catheters are employed to act as a conduit to help support microcatheter access. Traditional guide catheters designed for coronary or peripheral use (U.S. Pat. No. 5,180,376 & U.S. Pat. No. 5,484,425 Fischell, U.S. Pat. No. 5,045,072 Castillo, U.S. Pat. No. 5,279,596 Castaneda, U.S. Pat. No. 5,454,795 Samson and U.S. Pat. No. 5,733,400 Gold), typically are not positioned above the skull base and limit their effectiveness in supporting microcatheters in the distal cerebrovasculature. Newer distal access guide catheters have been developed which are slightly longer, thinner, a bit more flexible than the early generations, but are constructed with the same manufacturing techniques as described in U.S. Pat. No. 5,180,376 & U.S. Pat. No. 5,484,425 Fischell, U.S. Pat. No. 5,045,072 Castillo, U.S. Pat. No. 5,279,596 Castaneda, U.S. Pat. No. 5,454,795 Samson and U.S. Pat. No. 5,733,400 Gold, but have not solved the kinking problem (Neuron Penumbra Recall—Oct. 2, 2009).

SUMMARY OF THE INVENTION

In accordance with one aspect of the present invention, there is provided a catheter device comprising a tubular member, an inner liner and an outer cover. The tubular member has an inner lumen and an outer surface. The tubular member comprises a metal helix having a helical gap and a polymeric material disposed within the helical gap. The inner liner extends through the lumen of the tubular member and defines an inner lumen of the catheter. The outer covering is disposed on the outer surface of the tubular member. The dimension(s) of the metal helix and/or the width of the helical gap may be constant over the entire length of the catheter or may be varied to provide for regionalized differences in flexural properties and/or kink resistance. In some embodiments, the components of the catheter device may be sized and constructed such that a distal region of the catheter device has an inner diameter to wall thickness ratio of from about 16:1 to about 24:1 (in some embodiments preferably about 16:1) and the following properties: a) a lateral flexibility of greater than 1200 degree/in-lb and/or b) a kink radius of about 0.174 inch+/−0.008 inch or less and/or a tensile strength of 22N UTS.

Further in accordance with the present invention, there is provided a method for manufacturing a catheter comprising the steps of: A) forming or obtaining a metal helix having a helical gap; B) causing polymeric material to be disposed within the helical gap such that the polymeric material and the metal helix, in combination, form a tubular member having an outer surface and a lumen; C) causing an inner liner to be disposed within the lumen of the tubular member; and D) causing an outer cover to be disposed on the outer surface of the tubular member. In some embodiments, the polymeric material may be a cast polyurethane material, such as a polyurethane adhesive.

Still further in accordance with the present invention, there is provided a method for treating or diagnosing a disorder in a human or animal subject, said method comprising the steps of A) inserting into the subject's vasculature a catheter device of the type described herein and B) delivering a substance or device through the lumen of the catheter device and using the substance or device to treat or diagnose the disorder. In some embodiments of this method, the catheter device may be advanced into a blood vessel located within the subjects skull or which carry blood to or from the brain. Examples of blood vessels into which the catheter devices of the present invention may be advanced include the carotid arteries, cerebral arteries, anterior cerebral artery, middle cerebral artery and posterior cerebral artery.

Still further in accordance with the invention there is provided a system useable for performing a therapeutic or diagnostic task at a location within the body of a human or animal subject, such system comprising a) distal access aspiration guide catheter that has a proximal portion, a distal portion, a lumen and a distal end opening, said catheter distal tip being highly kink resistant, flexible, and with an inner diameter to catheter wall ratio of greater than 16 with a lateral stiffness (Flexibility) of greater than 1200.degree./in-lb. and b) working devices that are advance-able though the lumen of the catheter and out of its distal opening, said working devices being useable to perform the therapeutic or diagnostic task. Examples of the types of working devices that may be used in this system include but are but are not limited to; i) devices for removing thrombus or other obstructive matter from body lumens and/or to the distal opening of the access aspiration guide catheter for aspiration, ii) flow restoration devices useable to facilitate flow of a fluid though or around an obstruction within a body lumen and iii) devices for deploying or delivering implants (e.g., implantable occlusion coils or implantable embolic devices) and/or iv) devices that temporarily occlude the lumen.

Still further in accordance with the invention, there is provided a method for performing a therapeutic or diagnostic task at a location within the body of a human or animal subject, such method comprising the steps of: a) inserting into the subject's body a catheter that has a proximal portion, a distal portion, a lumen and a distal end opening, said catheter being catheter distal tip being highly kink resistant, flexible, and with a catheter inner diameter to catheter wall ratio of greater than 16 with a lateral stiffness (Flexibility) of greater than 1200.degree./in-lb. b) positioning the distal end opening of the catheter distally in a desired body lumen and c) advancing a working device though the lumen of the catheter and out of its distal opening; and, using the working device to perform the therapeutic or diagnostic task. Examples of the types of working devices that may be used in this method include but are but are not limited to; i) devices for removing thrombus or other obstructive matter from body lumens and/or to the distal access aspiration guide catheter for aspiration, ii) flow restoration devices useable to facilitate flow of a fluid though or around an obstruction within a body lumen and iii) devices for deploying or delivering implants (e.g., implantable occlusion coils or implantable embolic devices) and/or iv) devices that temporary occlude the lumen.

Still further in accordance with the invention there is provided a method for removing obstructive matter from a body lumen, such method comprising the steps of a) distal access aspiration guide catheter that has a proximal portion, a distal portion, a lumen and a distal end opening, said catheter distal tip being highly kink resistant, flexible, and with a inner diameter to catheter wall ratio of >16 and; b) positioning the catheter, such that its distal end opening is within a body lumen; c) moving obstructive matter through the distal end opening and into the lumen of the catheter; and d) removing the catheter along with the obstructive matter that has been moved into the lumen of the catheter. In some embodiments, negative pressure may be applied through the lumen of the catheter to aspirate obstructive matter through the distal end opening and into the lumen of the catheter. In some embodiments, Step C of the method may comprise advancing an obstructive matter moving device (e.g., an embolectomy or thrombectomy device) from the catheter and using the obstructive matter-moving device to move obstructive matter through the distal end opening and into the lumen of the catheter.

For purposes of summarizing the invention, certain aspects, embodiments, variations, details, elements, examples, advantages, and novel features of the inventions are described herein. It is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein. These and other objects and advantages of the present invention will be more apparent from the following detailed description taken in conjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS AND OTHER APPENDICES

Appended to, and forming a part of, this provisional patent application are the following materials:

FIG. 1 is a side, partially cut-away view of one embodiment of a catheter device of the present invention having three sections.

FIG. 1A is a table containing component information and specifications for the embodiment shown in FIG. 1,

FIG. 2 is a side, partially cutaway view of one embodiment of a catheter device of the present invention having four sections.

FIG. 2A is a table containing component information and specifications for the embodiment shown in FIG. 2.

FIG. 3 is a bar graph comparing lateral flexibility/stiffness of a catheter 100 of the present invention (as seen in FIG. 1) with a another guide catheter device.

FIG. 4 is a pictorial comparison illustrating the kink resistance of a catheter 100 of the present invention (as seen in FIG. 1) with a another guide catheter device.

FIG. 5 is a table showing examples of inner diameter to wall thickness ratios for catheters 100, 100 a of the present invention in sizes ranging from 4 French to 8 French.

DETAILED DESCRIPTION AND EXAMPLES

The following detailed description and the accompanying drawings to which it refers are intended to describe some, but not necessarily all, examples or embodiments of the invention. The described embodiments are to be considered in all respects only as illustrative and not restrictive. The contents of this detailed description and the accompanying drawings do not limit the scope of the invention in any way.

As used herein, the terms proximal and distal refer to a direction or a position along a longitudinal axis of a catheter or medical instrument. Proximal refers to the end of the catheter or medical instrument closer to the operator, while distal refers to the end of the catheter or medical instrument closer to the patient. For example, a first point is proximal to a second point if it is closer to the operator end of the catheter or medical instrument than the second point. The measurement term French, abbreviated Fr or F, is defined as three times the diameter of a device as measured in mm. Thus, a 3 mm diameter catheter is 9 French in diameter.

There is provided in accordance with one aspect of the present invention, a method for accessing regions of the vasculature through tortuous anatomy. Such vasculature includes the cerebrovasculature wherein access to the circle of Willis and beyond is exceedingly difficult due to the carotid siphon or vertebral artery anatomy that must be traversed to reach such locations without undo trauma or vessel straightening. The method comprises the steps of providing a catheter having a proximal end, a distal end of the catheter is inserted into the artery, and the support is distally advanced. Negative pressure can be applied to the proximal end of the catheter or an affixed aspiration port, to draw the thromboembolic material into the distal section. Catheters and other instrumentation (Working devices) can be inserted through the distal access aspiration guide catheter within the vasculature to gain access to locations where flexibility, kink resistance, torqueability, and column strength are required.

Typical arteries may be, among other examples, the common carotid artery, the internal carotid artery, the carotid siphon, the circle of Willis, etc. Alternatively, the artery may be the middle cerebral artery or the anterior cerebral artery, or elsewhere in the brain.

The method may additionally comprise the steps of introducing oxygenated medium into the artery through the aspiration lumen, or infusing pharmaceutical agent into the artery through the aspiration lumen. The pharmaceutical agent may be a vasodilator such as nifedipine or nitroprusside. The pharmaceutical agent may alternatively comprise t-PA. The thromboembolic material may be located using intravascular ultrasound, or carotid Doppler imaging techniques.

In accordance with another aspect of the present invention, there is provided an intracranial aspiration catheter. In accordance with the present invention, there is provided a method of establishing a flow path through a catheter, positioned across a non-linear segment of vasculature.

In certain embodiments, the aspiration catheter can serve as an guide catheter for placement of the micro-catheter. The guide catheter is advanced to a target region in cooperation with a guidewire to allow for steering and manipulation through the vasculature. In an exemplary procedure, the guidewire and guide catheter are introduced into the vasculature at a site within a femoral or iliac artery. Using a Seldinger technique, or other percutaneous procedure, a hollow 18-Gauge needle can be introduced into a femoral artery via percutaneous procedure. A guidewire is next advanced through the hollow needle and into the arterial tree. The hollow needle is next removed and an introducer sheath is advanced into the arterial tree. The guide catheter is next advanced through the catheter introducer either through the same guidewire or through a larger guidewire suitable for aortic traverse. The guide catheter is advanced through the aortic arch, into a carotid artery, through the carotid siphon and into a region proximate the circle of Willis. The guide catheter, because of its flexibility and high kink resistance can easily inserted through tortuous anatomy beyond the carotid siphon or the vertebral and basilar arteries. Once properly placed, the guide catheter can be utilized as a large conduit for the insertion of other working devices. Because of its large inner diameter multiple devices can be inserted. The guide catheter can serve as an aspiration device and as a shield for retrieval of debris, thrombus, or other material from the vasculature.

The guide catheter is preferably terminated, at its proximal end, with a luer or hemostasis valve and optionally with a connector offering multiple access ports, each of which can be valved or be terminated with a stopcock, etc.

There is disclosed a distal access aspiration catheter 100 in accordance with one aspect of the present invention. Although primarily described in the context of distal access aspiration guide catheter with a single central lumen, catheters of the present invention can readily be modified to incorporate additional structures, such as permanent or removable column strength enhancing mandrels, two or more lumen such as to permit drug or irrigant infusion or radiation delivery or to supply inflation media to an inflatable balloon, or combinations of these features, as will be readily apparent to one of skill in the art in view of the disclosure herein. In addition, the present invention will be described primarily in the context of providing distal vascular access for other endovascular working devices and removing obstructive material from remote vasculature in the brain.

The catheters disclosed herein may readily be adapted for use throughout the body wherever it may be desirable to introduce a very flexible thin walled catheter and kink resistant, which provides a relatively large diameter aspiration or supported working channel. For example, catheter shafts in accordance with the present invention may be dimensioned for use throughout the coronary and peripheral vasculature, the gastrointestinal tract, the urethra, ureters, Fallopian tubes and other lumens and potential lumens, as well. The lumen structure of the present invention may also be used as a minimally invasive percutaneous tissue tract expander, such as for diagnostic or therapeutic access to a solid tissue target (e.g., breast biopsy or tissue excision).

FIG. 1 illustrates a side partial breakaway view of a guide catheter device 100. In this example, the guide catheter 100 comprises an elongate body having a proximal section 101, a medial section 102 and a distal section 103. A lumen 104 extends through the catheter 100. The elongate body of the catheter comprises an inner liner or sleeve 105, a first kink resistant member comprising a metalic helix 106, a second kink resistant member comprising a thermoset polymer material 107 is positioned within the helical gap of the metal helix 106, a distal outer cover 108 disposed on the distal section 103 and a proximal tubular cover 109 disposed on the proximal and medial sections. A luer or manifold 110 is provided on the proximal end of the elongate catheter body. Optionally, one or more radiographic marker(s) 112 may be positioned on or in the elongate catheter body, such as at the distal tip as shown in the example of FIG. 1. Certain specification and details of the catheter 100 shown in FIG. 1 are set forth in the table of FIG. 1A.

The polymers comprising the proximal tubular cover 108 and the distal tubular cover 109 are heat set using heat shrink tubing or other compression methodology and heat, such as that generated by a heated air flow source, radiant heat source, induction heater, radiofrequency heater, or the like. The metallic kink resistant member reinforcement 106 is a metallic structure, either of ribbon or flattened wire. The winds (i.e., helical convolutions) of the metallic kink resistant member 106 are disposed such that distributed flexibility can be generated a long the lengths of the catheter shaft. The helical gap within the metallic winds along with the thermoset set polymeric kink resistant member 107, can cause the flexibility to be substantially evenly distributed, or directed along a specific axis. The metal used in the metallic kink resistant member can be nitinol, stainless steel, cobalt-nickel alloy, titanium, or the like. The thermoset polymeric kink resistant member 107 may be thermoset urethane, or the like.

The kink resistant members 106 and 107 can beneficially be created such that the reinforcement becomes more flexible moving distally by changing the gap or thicknesses of these members. Additionally the flexibility can also be adjusted be changing the thicknesses and materials of the inner sleeve and outer tubular cover.

The proximal end of the catheter is additionally provided with luer or a manifold having one or more access ports as is known in the art. Generally, the manifold is provided with a guidewire port in an over-the-wire construction, an aspiration port, and a catheter insertion port. One or more of these features can be embodied within a single port. Alternatively, the aspiration port may be omitted if the procedure involves removal of the guidewire proximally from the guidewire port following placement of the aspiration catheter, and aspiration through the guidewire port. Additional access ports may be provided as needed, depending upon the functional capabilities of the catheter. The manifold may be injection molded from any of a variety of medical grade plastics, or formed in accordance with other techniques known in the art.

The proximal body segment will exhibit sufficient column strength to permit axial positioning of the catheter through a patient's vasculature. The catheter body may further comprise other components, such as radiopaque fillers; colorants; reinforcing materials; reinforcement layers, such as braids and helical reinforcement elements; or the like. In particular, the proximal body segment may be reinforced in order to enhance its column strength and torqueability while preferably limiting its wall thickness and outside diameter.

When present, an optional radiographic marker 112 will typically be provided at least at the distal end of the catheter 100. Other radiopaque markers may be provided elsewhere, such as on the support coil, if it is not already radiopaque. One embodiment of a radiopaque marker that may be used comprises a metal band, which is fully recessed within the distal end of the proximal body segment. Suitable marker bands can be produced from a variety of materials, including platinum, gold, and tungsten/rhenium alloy. Preferably, the radiopaque metal band will be recessed in an annular channel formed at the distal end of the proximal body segment.

Diameters outside of the preferred ranges may also be used, provided that the functional consequences of the diameter are acceptable for the intended purpose of the catheter. For example, the lower limit of the diameter for any portion of tubular body in a given application will be a function of the number of fluid or other functional lumen contained in the catheter, together with the acceptable minimum aspiration flow rate and collapse resistance.

Tubular body must have sufficient structural integrity (e.g., column strength or “pushability”) to permit the catheter to be advanced to distal locations without buckling or undesirable bending of the tubular body. The ability of the body to transmit torque may also be desirable, such as to avoid kinking upon rotation, to assist in steering. The tubular body, and particularly the distal section, may be provided with any of a variety of torque and/or column strength enhancing structures. For example, axially extending stiffening wires, spiral wrapped support layers, braided or woven reinforcement filaments may be built into or layered on the tubular body.

In many applications, the proximal section will not be required to traverse particularly low profile or tortuous arteries. For coronary vascular applications, for example, the proximal section will be mostly or entirely within the relatively large diameter guide catheter. The transition can be located on the catheter shaft to correspond approximately with the distal end of the guide catheter when the balloon and/or distal end is at the treatment site. For certain other applications, such as intracranial catheterizations, the distal section is preferably at least about 5 cm long and small enough in diameter to pass through vessels as small as 3 mm or 2 mm or smaller. Catheters for this application may have a proximal section length of between about 60 cm to about 150 cm and a distal section length of between about 5 cm to about 15 cm, and the distal section is able to track a tortuous path of at least about 5 cm through vessels of less than about 3 mm lumen ID.

The number of sections may vary. For example, FIG. 2 shows another embodiment of a catheter device 100 a having essentially the same components and construction described above with respect to the catheter of FIG. 1, except that this catheter 100 a has a first distal section 120 and a second distal section 122. The dimensions (e.g., width, thickness) of the metal helix 106 and/or the outer cover 109 may vary between the two distal sections 120, 122, thereby causing them to have different properties. Specific examples of those dimensions and other specifications for this catheter 100 a are shown in the table of FIG. 2A.

FIG. 3 is a bar graph comparing lateral flexibility/stiffness of a catheter 100 of the present invention (as seen in FIG. 1) with a another guide catheter device.

FIG. 4 shows photographs and data comparing kink resistance of a catheter 100 of the present invention (as seen in FIG. 1) with a another guide catheter device.

FIG. 5 is a table showing examples of inner diameter to wall thickness ratios for catheters 100, 100 a of the present invention in sizes ranging from 4 French to 8 French.

In some embodiments of the invention, an optional balloon, such as a compliant balloon formed of material such as latex, silicon, Chronoprene, Santoprene or other elastomers, may be positioned at or near the distal end of the elongate catheter body. Such optional balloon may be useful for occluding flow through the blood vessel in which the catheter is positioned when such flow occlusion is desired.

In at least some embodiments, the proximal section 101 will retain radial strength but provide lateral flexibility. Additionally, that section desirably has a lateral flexibility (Stiffness), such as would be measured by a Tinius-Olsen Stiffness Tester, of at least 1,200.degree. of deflection/inch-pound (measured at 20.degree.-30.degree, of deflection, 0.005 lb, over a 0.25″ span), preferably 2,500.degree. of deflection/inch-pound. We have additionally found that the radial compression strength of the section is quite high as compared to other distal sections found on comparable catheter distal sections.

Access for the catheter of the present invention can be achieved using conventional techniques through an incision on a peripheral artery, such as right femoral artery, left femoral artery, right radial artery, left radial artery, right brachial artery, left brachial artery, right axillary artery, left axillary artery, right subclavian artery, or left subclavian artery. An incision can also be made on right carotid artery or left carotid artery in emergency situations.

The construction disclosed herein is suitable for guide catheter as a stand-alone device. This construction results in a highly flexible device having high column strength, torqueability, kink-resistance, and tensile strength.

It is to be appreciated that the invention has been described hereabove with reference to certain examples or embodiments of the invention but that various additions, deletions, alterations and modifications may be made to those examples and embodiments without departing from the intended spirit and scope of the invention. For example, any element or attribute of one embodiment or example may be incorporated into or used with another embodiment or example, unless otherwise specified of if to do so would render the embodiment or example unsuitable for its intended use. Also, where the steps of a method or process have been described or listed in a particular order, the order of such steps may be changed unless otherwise specified or unless doing so would render the method or process unworkable for its intended purpose. All reasonable additions, deletions, modifications and alterations are to be considered equivalents of the described examples and embodiments and are to be included within the scope of the following claims. 

The invention claimed is:
 1. A catheter comprising: a catheter body comprising: an inner liner; an outer cover; a metal structure between the inner liner and the outer cover, the metal structure defining a helical gap; and a polymeric material positioned within the helical gap and between the inner liner and the outer cover, wherein the polymeric material comprises a thermoset polymer material, and wherein the polymeric material is different from the materials of the inner liner and outer cover, and wherein a distal section of the catheter body has an inner diameter to wall thickness ratio greater than or equal to 16:1.
 2. The catheter of claim 1, wherein the inner diameter to wall thickness ratio of the distal region of the catheter body is in a range of 16:1 to 24:1.
 3. The catheter of claim 1, wherein the distal section of the catheter body has a lateral flexibility of greater than or equal to 1200 degrees of deflection per pound-force inch.
 4. The catheter of claim 1, wherein the distal section of the catheter body comprises a first distal section and a second distal section distal to the first distal section, wherein the first distal section has a first lateral flexibility of greater than or equal to 1000 degrees of deflection per pound-force inch and the second distal section has a second lateral flexibility of greater than or equal to 1500 degrees of deflection per pound-force inch.
 5. The catheter of claim 1, wherein the distal section of the catheter body comprises a first distal section and a second distal section distal to the first distal section, wherein the first distal section has a first lateral flexibility of greater than or equal to 1500 degrees of deflection per pound-force inch and the second distal section has a second lateral flexibility of greater than or equal to 2500 degrees of deflection per pound-force inch.
 6. The catheter of claim 1, wherein the distal section of the catheter body has an Ultimate Tensile Strength of 22 Newtons.
 7. The catheter of claim 1, wherein the metal structure and the polymeric material extend to a distal end of the catheter body.
 8. The catheter of claim 1, wherein the metal structure comprises a nickel titanium alloy, stainless steel, cobalt-nickel alloy, or titanium.
 9. The catheter of claim 1, wherein the helical gap has a continuous width.
 10. The catheter of claim 1, wherein the helical gap varies in width over a length of the catheter body.
 11. The catheter of claim 10, wherein a proximal portion of the helical gap in a proximal section of the catheter body has a smaller width than a distal portion of the helical gap in the distal section of the catheter body.
 12. The catheter of claim 1, wherein the polymeric material comprises an elastomer.
 13. The catheter of claim 1, wherein the polymeric material comprises a thermoset polyurethane adhesive.
 14. The catheter of claim 1, further comprising braided or woven reinforcement filaments on the metal structure and the polymeric material.
 15. The catheter of claim 1, further comprising a balloon.
 16. The catheter of claim 1, further comprising a hydrophilic coating on an outer surface of the outer cover.
 17. A catheter comprising: an elongate body defining a lumen, the elongate body comprising: an inner liner; an outer cover; and a tubular member between the inner liner and the outer cover, the tubular member comprising: a metal helix defining a helical gap; and a thermoset polymeric material positioned within the helical gap, wherein the thermoset polymeric material is different from the materials of the inner liner and outer cover, and wherein a distal section of the elongate body has an inner diameter to wall thickness ratio greater than or equal to 16:1.
 18. The catheter of claim 17, wherein the distal section of the elongate body has a lateral flexibility of greater than or equal to 1200 degrees of deflection per pound-force inch.
 19. A method comprising: forming a catheter body, wherein forming the catheter body comprises: disposing polymeric material within a helical gap defined by a metal structure, wherein the polymeric material comprises a thermoset polymeric material; positioning an inner liner radially inward of the polymeric material and the metal structure; and positioning an outer cover over the polymeric material and the metal structure, wherein the polymeric material is different from the materials of the inner liner and outer cover, and wherein a distal section of the catheter body has an inner diameter to wall thickness ratio greater than or equal to 16:1.
 20. The method of claim 19, wherein positioning the inner liner radially inward of the polymeric material and the metal structure comprises casting a flowable polymeric material into the helical gap and solidifying the flowable polymeric material over the inner liner.
 21. The method of claim 19, wherein the distal section of the catheter body has a lateral flexibility of greater than or equal to 1200 degrees of deflection per pound-force inch.
 22. The method of claim 19, further comprising applying a hydrophilic coating to an outer surface of the outer cover. 